Coloring maps 2 (1)
To force the use of 6 colors we do not need 32 regions, since 8 suffice:
Analogously, here is a sequence that shows how seven colors are needed to color a map with 10 regions:
Which is the minimal number of regions in a map that needs 8 colors to be colored incrementally? Is there a general formula or a general map structure that answers this question?